^This often comes up, but please note, the actual phrase he said in the Japanese were that there are only "five types" of DFs known to fly.
Not five.
We don't know if he actually only meant five devil fruits, or the entire family of "bird Zoans" are simply a single type. They are, after all, subgrouped into each models. And the way things are going, It seems rather logical to assume so. Regardless, Oda has left an excuse if he decides so anyways.
